1. Field of the Invention
The present invention relates to prophylactic and therapeutic agents for cataracts and radiation-protecting agents comprising glutathione monoalkyl esters. In another aspect, the invention is directed to a method for the prevention and treatment of cataracts using the agents of this invention.
2. Description of the Related Art
Cataracts refer to a state in which the stromatic lens has decreased optical permeability caused by the generation and the deposition of certain materials, which results in the decrease of the amount of light which can reach the interior of eyes, and as a result the visual acuity is decreased.
Cataracts may be classified as congenital, senile, diabetic, complicated cataracts, and the like. The factors that cause such a state are many and X-ray radiation is but one of these factors.
As therapeutic agents for cataracts, there have been hitherto applied an operation therapy and a drug therapy such as the administration of eye-drops containing cataline or glutathione and of KI or vitamin C, and the like but the therapy except for an operation therapy have some troubles in the fundamental treatment of cataracts.
The glutathione monoalkyl esters are alkyl esters of glutathione with respect to its glycine carboxyl group. It has been found that these compounds are useful as therapeutic agents for cataracts, in particular, as therapeutic agents for cataracts induced by radioactive rays or X-ray radiation.
Also, the effect is remarkably superior to that of glutathione-containing eye-drops described above, contrary to the expectation of a person skilled in the relevant art.